A variety of countercurrent chromatographic methods developed in the past (see Y. Ito, Development of Countercurrent Chromatography, Anal. Chem., 5b,534A, 1984) utilize a stationary phase that is permanently retained in the separation column through which the mobile phase is continuously eluted. This ordinary elution mode, common with many other chromatographic methods, is applied to a batch separation to yield a chromatographic separation of solutes locally charged as a discrete sample volume. Versatility of these methods, however, can be further increased if the system permits continuous separation by continuous sample feeding.
An application of countercurrent chromatography is foam separation. Although the foam separation method has been widely used during the past fifty years (see P. Somasundaran, Foam Separation Methods, Sep. Purif. Methods, 1, 117, 1972), the method has remained rather primitive and insufficient, thus largely limiting its application to use in research laboratories.
A developed countercurrent chromatographic method called high speed countercurrent chromatography (CCC), see U.S. Pat. No. 4,430,216, utilizes a particular combination of coil orientation and planetary motion to produce a unique hydrodynamic effect which permits a true countercurrent flow of the two solvent phases through the coiled column. With a proper column design the two phases can be simultaneously eluted through the column in opposite directions while the sample solution is continuously fed to the middle portion of the column. This dual countercurrent system provides a rich domain of applications such as continuous extraction, enrichment and stripping as well as continuous separation of solutes and particles.